The present invention relates to a low voltage power supply and more particularly to one which is used in a two wire thermostat circuit to provide efficient low power dissipation in both the "on" and "off" states of the thermostat. The present invention uses switching devices to provide a DC voltage regulation. The switches operate in a shunting manner to minimize AC voltage drop in the load during a "on" condition so as not to reduce the supply voltage significantly. In the "off" state the switches are in series to minimize the AC load currents and any resulting DC supply dissipation.